Retractable furnace slurry sprayer



Dec. 7, 1965 R. CHAPPELL RETRACTABLE FURNACE SLURRY SPRAYER 3Sheets-Sheet 1 (Filed May 21 1963 INVENTOR. Z 4Ze/f 167477 7/.

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Dec. 7, 1965 R. E. CHAPPELL RETRACTABLE FURNACE SLURRY SPRAYER 3Sheets-Sheet 5 Filed May 21, 1963 United States Patent M 3,221,994RETRACTAELE FURNACE SLURRY SPRAYER Robert E. Chappell, Lmeaster, Ohio,assignor to Diamond Power Specialty Corporation, Lancaster, ()hio, acorporation of Ghio Filed May 21, 1963, Ser. No. 231,971 3 Qlairns. (Cl.239186) The present invention broadly pertains to spraying apparatus andmore particularly to an improved extractable type sprayer adapted formounting on a wall of a heat exchanger apparatus for automaticallyspraying a liquid or slurry of a chemical additive into the interior ofthe boiler.

Various techniques and apparatuses have heretofore been used or proposedfor use in connection with the injection of chemical additives in theform of solutions or suspensions into the interior of various types ofheat ex.- changer apparatuses. Some of these techniques include theaddition of the additive in the fuel for discharge through the burnernozzles, the manual spraying of the additive at selected locations, aswell as incorporating additive conduits in conventional soot blowersemployed for discharging a high pressure blowing medium against the heatexchanger surfaces for effecting a dislodgement of the soot, slag, andother extraneous deposits thereon. The latter technique has been foundeminently satisfactory in most heat exchanger installations. In someinstances, however, it has been found desirable to inject such chemicaladditives at locations which are not serviced by soot blowers equippedwith additive injecting means or alternatively, to supplement theadditive injected by the soot blower. The apparatus comprising thepresent invention is particularly applicable for adapting a heatexchanger apparatus with a chemical additive system withoutnecessitating a modification of the cleaning equipment originallyinstalled.

The furnace sprayer comprising the present invention is particularlyapplicable for injecting chemical additives such as magnesium oxideand/or calcium oxide in the form of an aqueous slurry against the heatexchanger surfaces of direct-fired combustion apparatus to effect areduction in the corrosion of such heat exchanger surfaces and toincrease the ease by which the deposits such as soot and slag can beremoved therefrom by conventional boiler cleaning equipment. Effectivecontrol of corrosion and slag deposition requires periodic treatment ofthe heat exchanger surfaces with a prescribed quantity of the slurryadditive. The automatic operation of the furnace sprayer comprising thepresent invention enables it to be readily adapted to an automaticsequentially phased control system incorporating a plurality of suchsprayers which can be operated in a preselected sequentially phasesequence at preselected time intervals. Automatic systems of this typesubstantially eliminate the problems associated with a haphazardtreatment of heat exchanger surfaces as encountered by manually operatedsprayers which require considerable attention and manpower to providethe requisite treating function.

It is accordingly a principal object of the present invention to providean automatic remotely actuable furnace sprayer which overcomes theproblems and disadvantages associated with manual type sprayers of thetypes heretofore known.

Another object of the present invention is to provide an improvedfurnace sprayer which on actuation is operative to automatically efifecta discharge of a liquid chemical additive in the form of a fine sizedspray into the interior of a heat exchanger apparatus and thereafter isautomatically retracted and the interior of the spray tube is purged bya high pressure air blast to remove any residual liquid chemicalthereon.

3,221,994 Patented Dec. 7, 1965 Still another object of the presentinvention is to provide an improved furnace sprayer which is of simpledesign, of durable operation, of versatile installation, and ofeconomical manufacture and operation.

The foregoing and other objects and advantages of the present inventionare achieved by a furnace sprayer adapted for mounting on the wall of aheat exchanger apparatus and including a spray tube formed with a nozzlein the forward end thereof which is reciprocable to and from aninoperative retracted position to an operative projected position andwhich spray tube incorporates actuator means thereon for automaticallyactuating valve means responsive to the reciprocating movement thereoffor starting and stopping the flow of liquid treating additive into thespray tube and for starting and stopping a pressurized purging gasmaintaining the interior of the spray tube in a substantially cleancondition preparatory to the next operating cycle. It will beappreciated that while the furnace sprayer comprising the presentinvention is particularly applicable for injecting a treating slurryagainst the heat exchanger surfaces of direct-fired heat exchangerapparatus, the sprayer can also be satisfactorily employed in otherinstallations wherein periodic automatic spray application of fluids isrequired.

The manner of accomplishing the foregoing objects, and other objects andfeatures of the invention, will become apparent from the followingdetailed description of an embodiment of the invention when read withreference to the accompanying drawings in which:

FIGURE 1 is a side elevation view partly in section of a slurry furnacesprayer constructed in accordance with the preferred embodiment of thepresent invention removably mounted on the exterior surface of a boiler;

FIG. 2 is a magnified plan view of the furnace sprayer shown in FIGURE1;

FIG. 3 is a side elevation view of the furnace sprayer shown in FIGURE2;

FIG. 4 is a transverse vertical sectional view through the furnacesprayer shown in FIGURE 3 and taken along the line 44 thereof;

FIG. 5 is a perspective view of the underside of the furnace sprayershown in FIGURES 13.

FIG. 6 is an enlarged plan view partly in section and partly in phantomillustrating in particular the arrangement of the piping for supplyingpressurized air to the furnace sprayer; and

PEG. 7 is a magnified fragmentary sectional view of an orifice port inthe piping arrangement shown in FIG- URE 6 and taken along the line 7-7thereof.

Referring now in detail to the drawings, the slurry furnace sprayercomprising the present invention comprises a frame including alongitudinally extending member 10 of an inverted U-shaped configurationwhich is securely affixed at its forward end to a mounting plate 12. Apair of gussets 14 are preferably rigidly welded to the mounting plate12 and member if) for reinforcing the framework. The mounting plate 12is formed with a plurality of apertures 16 therethrough for removablysecuring the furnace sprayer such as by means of bolts to a plate 18mounted in a port 20 of a wall 22 of the heat exchanger apparatus. Theplate 18 and the mounting plate 12 of the sprayer framework is formedwith a pair of aligned holes 24 through which the nozzle end portion ofa spray tube 26 projects and is movable therethrough during theprojecting and retracting movement of the spray tube.

The forward end portion of the spray tube 26, as best seen in FIGURES 2and 3, is formed with a nozzle head 28 having at least one small hole(not shown) therein through which the fluid chemical additive isdischarged during operation of the sprayer unit. The particular type ofnozzle head 28 and the disposition of the discharge holes therein can beselected so as to provide the desired spray configuration in accordancewith the disposition of the heat exchanger surfaces to be treated.

In the exemplary installation shown in FIGURE 1, the spray tube andnozzle head are disposed in the fully retracted position wherein thenozzle head is located within the port and out of direct contact withthe hot combustion gases within the interior of the boiler. Any heatabsorbed by the forward face of the nozzle head 28 is quickly conductedoutwardly along the spray tube which is located exteriorly of the boilerand at a relatively low ambient temperature. During operation of thefurnace sprayer, the spray tube and nozzle head are reciprocated to afully projected position as shown in phantom in FIG URE 1 wherein thenozzle head is disposed beyond the water wall tubes 30 disposed alongthe inner surface of the boiler wall 22. While in the fully projectedposition a liquid treating additive such as an aqueous slurry of calciumoxide and/or magnesium oxide for example, is discharged from the nozzlehead in a manner such that the fine sized droplets impinge on the heatexchanger surfaces to be treated.

The reciprocation of the spray tube 26 to and from the inoperativeposition and the projected position is achieved by a double actingair-actuated cylinder 32 which is affixed to the inner surface of a web34 of the member 10 such as by means of bolts 36 and is positioned withits piston rod 38 disposed in substantial longitudinal alignment withthe hole 24 in the mounting plate 12. The end of the piston rod 38 issecured to a T fitting 40 into the other end of which the rearward endof the spray tube 26 is threadably disposed in pressure-sealingrelationship. A slide block 42 is adjustably afiixed to the rearward endof the spray tube 26 adjacent to the T fitting 40 such as by means of aset screw 43 as may be best seen in FIGURE 4.

An actuator pin 44 is threadably engaged in the slide block 42 andprojects upwardly through a longitudinal groove or slot 46 extendingalong the forward portion of the web 34 of the member 10. The actuatorpin 44 is movable along the slot 46 in response to the reciprocatingtravel of the spray tube and during which travel the actuator pin coactswith and pivotally rotates a bifurcated cam 48 of an air valve 50 and abifurcated cam 52 of a liquid slurry valve 54. To avoid the accumulationof dust and other extraneous deposits on the cams 48, 52, a cover shield55 is preferably mounted on the frame as best shown in FIGS. 3 and 4.

The cams 48, 52 as best seen in FIGURES 2-4 are oriented relative to theslot 46 and actuator pin 44 so as to be moved from the positions asshown in solid lines in FIGURE 2 to the positions as shown in phantomwhich are disposed approximately 90 from the original position shown.Each of the earns 48, 52 are provided with an inwardly extending slot 56which flares outwardly at the outer ends thereof indicated at 58 tofacilitate engagement and disengagement with the actuator pin 44. Thecam 48 when in the position as shown in solid lines in FIGURE 2 placesthe air valve 50 in the open position. Movement of the cam 48 from theposition as shown in solid lines to the position as shown in phantomeffects a closing of the air valve 50. On the other hand, when the cam52 is in the position as shown in solid lines in FIGURE 2, the slurryvalve 54 is disposed in the closed position. Rotation of the cam 52 tothe position as shown in phantom in FIGURE 2, elfects an opening of theslurry valve 54.

The supply of an aqueous slurry or other suitable liquid additivechemical to the interior of the spray tube is achieved by a main supplyheader 60 disposed exteriorly of the wall of the boiler to which asupply pipe 62 is connected for supplying slurry to each individualfurnace sprayer unit. A main shutotf valve 64 is incorporated in eachsupply pipe 62 for manually shutting off the supply of slurry to thespray unit as may be required from time to time to permit service of theunit. The supply pipe 62 is connected to the inlet side of the slurryvalve 54 and the outlet of the slurry valve is connected to a T fitting66 by means of a pipe 67 which is clamped to the member 10 by means of aU-bolt 69. The outlet of the T fitting 66 is connected by means of aflexible conduit or hose 68 to the T fitting 40 at the rear end of thespray tube. The flexible hose 68 enables unrestricted reciprocatingmovement of the spray tube relative to the framework of the spray unit.

The other side of the T fitting 66 is connected to the outlet side ofthe air valve 50 by means of a pipe or tube 70. The inlet side of theair valve 50 is connected to a check valve 72 which in turn is connectedto the outlet side of a chamber or air pressure accumulator 74 which isclamped to the side of the frame member 10 by means of a U-bolt 75. Thecheck valve 72 is oriented so as to prevent fiow of treating slurry intothe accumulator 74 and attendant tubing network in the event ofmalfunction of the air valve 50 or slurry valve 54.

The air pressure accumulator 74 is provided with a T fitting 76, as bestshown in FIGURES 5 and 6, mounted on the wall thereof intermediate toits ends. Each of the sides of the T fitting 76 is connected to a checkvalve 78, 80 which are oriented to permit the flow of air into but notout of the accumulator. The inlet side of the check valve 78 isconnected by means of a tube 82 to a T fitting 84 mounted on anddisposed in communication with the rod end of the pneumatic cylinder 32.The tube 82 is connected by means of a tube fitting 86 to the T fitting84 and is provided at that connection with an orifice disc 88 torestrict the flow of air to the accumulator. The other branch of the Tfitting 84 is connected by means of a tube 99 to an outlet port 92 of asolenoid actuated control valve 94.

The other check valve 80 connected to the T fitting 76 mounted on thepressure accumulator is connected at its inlet side by means of a tube96 to a T fitting 98 mounted on and disposed in communication with theblank end of the pneumatic cylinder 32. The tube 96 is connected to theT fitting 98 in a manner similar to the connection between the tube 82and fitting 84 employing an orifice disc 100 as best seen in FIG. 7 torestrict the flow of air therethrough. The other outlet branch of the Tfitting 98 is connected by means of a tube 102 to a T fitting 104connected to a second outlet port 106 of the control valve 94. The otherbranch of the T fitting 104 is provided with an orifice disc 108 for apurpose subsequently to be described.

The control valve 94 is of the solenoid actuable type well known in theart and is formed with the first outlet port 92 and second outlet port106 which are connected to the pneumatic cylinder and pressureaccumulator in a manner as previously described and as best seen in FIG-URE 6. The control valve 94 is also formed with an inlet port 110 whichis adapted to be connected by means of a tube 112 to a source of highpressure air which is operable to effect pneumatic actuation of the aircylinder 32, for purging the interior of the spray tube at thecompletion of a spraying cycle, and for supplying a continuous lowvolume stream of air for discharge through the nozzle head during theperiod of inoperation of the spray unit maintaining the nozzle holesopen and for cooling the spray tube and the nozzle head thereon. Thecontrol valve 94 incorporates a resiliently biased valve mechanismtherein which when the solenoid is in the deenergized condition, placesthe outlet port 92 in communication with the inlet port 110 maintaininga positive pressure at the rod end of the cylinder 32 and therebymaintaining the spray tube in the fully retracted position. At the sametime a continuous bleed of air flow passes through the orifice disc 88through the air pressure accumulator for discharge into the spray tubeand then out through the holes in the nozzle head thereon. Uponenergization of the control valve 94, the valve mechanism is moved so asto place the inlet port 110 in communication with the outlet port 106applying high pressure air to the blank end of the cylinder effectingmovement of the piston rod and spray tube to the fully projectedposition while simultaneously effecting a buildup of pressure within thepressure accumulator.

It will be apparent from the foregoing that automatic control of thefurnace spray unit is achieved simply by energizing the solenoid of thecontrol valve 94 for a preselected time period at the expiration ofwhich the deenergization of the solenoid causes the spray tube toautomatically retract and to be purged of residual slurry thereinplacing it in a standby condition for the next operating cycle. In viewof the simplicity provided in accordance with the spray unit comprisingthe present invention, a plurality of such units can readily beincorporated in a control system providing for a sequentially phasedoperation of each unit in a preselected sequence. Suitable electricaltiming means can be incorporated in such a system for energizing eachcontrol valve and maintaining that valve energized for a preselectedtime period to enable the injection of a prescribed quantity of liquidadditive into the interior of the heat exchanger apparatus.Alternatively, each unit can be energized remotely such as by a controlbutton on the master operating panel which may incorporate a suitableadjustable time delay relay for maintaining that spray unit energizedfor a selected time interval.

The operation of the spray unit will now be described with particularreference to FIGURES 2, 5, and 6. With the furnace spray unit in astandby condition, the spray tube 26 is in the fully retracted positionand the cams 52 and 43 are in the positions as shown in solid lines inFIG- URE 2 such that the slurry valve 54 is closed and the air valve 50is open. In this standby condition, high pressure actuating air suppliedfrom the supply line 112 to the control valve 94 is transmitted from theoutlet port 92 to the rod end of the air cylinder 32 by means of the Tfitting 84, maintaining a positive pressure against the piston holdingthe spray tube in the retracted position. The air in the T fitting S4bleeds through the orifice disc 88 passing through the tube 82 and checkvalve 78 into the pressure accumulator 74 from which it is dischargedthrough the check valve 72 and open air valve 48 through the tube 70 andT fitting 66 into the flexible hose 68 connected to the T fitting 40 atthe rearward end of the spray tube 26. This constant trickle of air isdischarged through the nozzle head 28 serving the dual function ofmaintaining the nozzle ports clear and cooling the nozzle head andforward end portion of the spray tube during inoperation.

The commencement of the operating cycle of the spray unit is simplyachieved by energizing the solenoid of the control valve 94 which movesits valve component so as to close communication between the inlet port110 and outlet port 92 and open communication between the inlet port 110and outlet port 106. Accordingly, high pressure actuating air isdiverted from the rod end of the air cylinder 32 to the blank endthereof through the tube 102 and T fitting 98 whereupon the piston rod38 and the spray tube connected thereto commence their projectingtravel. During the projecting travel of the piston rod 38, the air inthe rod end of the cylinder is discharged out through the T fitting 84and aperture disc 88 and passes into the accumulator 74 by means of thetube 82, check valve 78 and T fitting 76. The orifice disc 88 providessufiicient restriction so as to provide a cushioning effect andpreventing the piston from moving too rapidly toward the fully projectedposition. The air thus entering the accumulator 74 is discharged intothe spray tube until such time that the air valve 50 is closed inresponse to the advancing movement of the spray tube. With the controlvalve 94 in this position, the quantity of air which is dischargedthrough the orifice disc 108 in the T fitting 104 is negligible incomparison to that which is transmitted through the tube 102 into theblank end of the cylinder 32 efiecting forward movement of the pistontherein.

As the spray tube moves toward the projected position,

the actuator pin 44, as best seen in FIGURE 2, contacts the slot 56 ofthe cam 48 moving it from the position as shown in solid lines to theposition as shown in phantom effecting thereby a closing of the airvalve 50. Upon a closing of the air valve 50, the air pressuretransmitted through the orifice disc 88 through the tube 82 and throughthe orifice disc 100 through the tube 96 into the pressure accumlator 74effects a progressive buildup of air pressure therein.

During further continued projecting travel of the spray tube, theactuator pin 44 coacts with the cam 52 effecting a movement thereof fromthe position as shown in solid lines in FIGURE 2 to the position asshown in phantom whereupon the slurry valve 54 is opened. Accordingly,the liquid treating additive such as an aqueous slurry supplied from thesupply header 6% through the open shutoff valve 64 passes through theslurry valve 54 and T fitting 65 through the flexible hose 68 and isdischarged into the T fitting 40 at the rearward end of the spray tube26. The pressurized liquid additive is discharged from the nozzle head28 with the spray tube in substantially the fully projected position asshown in phantom in FIGURE 1. The spray tube is maintained in the fullyprojected position by the positive pressure applied to the blank end ofthe pneumatic cylinder 32. While in the fully projected position, airpressure continues to accumulate in the pressure accumulator 74 via thebleed of air passing through the orifice disc 1%, tube 96 and checkvalve and eventually approaches the pressure of the air supplied throughthe supply tube 112.

At the expiration of the spray period, as determined by a suitabletimer, for example, the solenoid of the control valve 94 is deenergizedeffecting a movement of the valve component therein so as to place theinlet port 110 in communication with the outlet port 92 and to closecommunication between the inlet port 119 and outlet port 106.Accordingly, pressurized air is directed into the rod end of thepneumatic cylinder 32 through the tube and T fitting 84 effecting aninitiation of the retracting movement of the spray tube. During theretracting movement of the piston in the pneumatic cylinder 32 the blankend of the cylinder is vented through the T fitting 98 and tube 102 andthe air is discharged through the orifice disc 108 providing sufficientrestriction so as to retard and cushion the retracting movement thereof.

As the spray tube retracts the actuator pin 44 coacts with the cam 52moving it from the position as shown in phantom in FIGURE 2 to theposition as shown in solid lines effecting thereby a closing of theslurry valve 54. Accordingly, the flow of slurry to the spray tube ishalted. During the further retracting movement of the spray tube, theactuator pin 44 coacts with the cam 48 moving it from the position asshown in phantom in FIGURE 2 to the position as shown in solid lineseffecting an opening of the air valve 56. As the air valve 50 is opened,the

accumulated air pressure in the pressure accumulator 74 is dischargedthrough the check valve 72, tube 70, T fitting 66, flexible hose 68 andT fitting 40 into the rearward end of the spray tube 26. This highvolume surge of pressurized air serves to purge the residuaiy slurry orliquid additive in the supply conduits and spray tube preventing anyresidual accumulation therein which might oiherwise have a tendency tofoul the nozzle ports.

\Vhen the spray tube attains its fully retracted position and at thecompletion of the discharge of the air from the pressure accumulator 74,a continuous trickle of air is discharged from the spray tube asprovided by the orifice disc 88 in a manner as previously described. Thefurnace sprayer unit is again in the standby condition preparatory toits next operating cycle.

While it will be apparent that the embodiments of the invention hereindisclosed are well calculated to fulfill the objects of the invention,it will be appreciated that the invention is susceptible tomodification, variation and change Without departing from the properscope or fair meaning of the subjoined claims.

What is claimed is:

1. A spray apparatus comprising a frame, a spray tube movably mounted onsaid frame and formed with a nozzle in the forward end portion thereof,an air operated means connected to said spray tube for effectingreciprocation thereof to and from a retracted position and a projectedposition, first conduit means including a first valve for supplying apressurized liquid additive to said spray tube, second conduit meansincluding a second valve for supplying pressurized air to said spraytube, supply means including control means for supplying pressurized airto said air operated means and said second conduit means, coacting meanson said spray tube and said first and said second valve for engaging andclosing said second valve and thereafter engaging and opening said firstvalve in response to the projecting travel of said spray tube and forclosing said first valve and opening said second valve in response tothe retracting travel of said spray tube, pressure accumulating meansdisposed in communicaation with said supply means and said secondconduit means for accumulating air under pressure upon closing of saidsecond valve and for discharging the accumulated air and purging saidspray tube upon the opening of said second valve.

2. A spray apparatus comprising a frame, a spray tube movably mounted onsaid frame and formed with a nozzle in the forward end portion thereof,an air cylinder connected to said spray tube for effecting reciprocationthereof to and from a retracted position and a projected position, firstconduit means including a first valve for supplying a pressurized liquidadditive to said spray tube, second conduit means including a secondvalve for supplying pressurized air to said spray tube, supply meansincluding control means for supplying pressurized air to said cylinderand said second conduit means, coacting means on said spray tube andsaid first and said second valve for engaging and closing said secondvalve and thereafter engaging and opening said first valve in responseto the projecting travel of said spray tube and for closing said firstvalve and thereafter opening said second valve in response to theretracting travel of said spray tube, a chamber on said frame disposedin communication with said supply means and said second conduit meansfor accumulating air under pressure upon closing of said second valveand for discharging the accumulated air and purging said spray tube uponthe opening of said second valve and for supplying a continuous trickleof air to said spray tube while in said retracted position.

3. A furnace sprayer comprising a frame, a spray tube movably andguidably mounted on said frame and formed with a nozzle in the forwardend portion thereof, a double acting air cylinder connected to saidspray tube for efifecting longitudinal reciprocation thereof to and froma retracted inoperative position and a projected operative position,first conduit means including a first valve for supplying a pressurizedliquid additive to said spray tube, second conduit means including asecond valve for supplying pressurized air to said spray tube, supplymeans including a remotely actuable control valve for supplyingpressurized air to said cylinder and said second conduit means, actuatormeans on said spray tube, a first cam on said first valve and a secondcam on said second valve and longitudinally spaced from said first cam,said actuator means operable to contact and actuate said first and saidsecond cam for sequentially closing said second valve and thereafteropening said first valve in response to the projecting travel of saidspray tube and for closing said first valve and thereafter opening saidsecond valve in response to the retracting travel of said spray tube, achamber on said frame disposed in communication with said supply meansand said second conduit means for accumulating air under pressure uponclosing of said second valve and for discharging the accumulated air andpurging said spray tube upon the opening of said second valve.

References Cited by the Examiner FOREIGN PATENTS 601,617 7/1960 Canada.

EVERETT W. KIRBY, Primary Examiner.

1. A SPRAY APPARATUS COMPRISING A FRAME, A SPRAY TUBE MOVABLY MOUNTED ONSAID FRAME AND FORMED WITH A NOZZLE IN THE FORWARD END PORTION THEREOF,AN AIR OPERATED MEANS CONNECTED TO SAID SPRAY TUBE FOR EFFECTINGRECIPROCATION THEREOF TO AND FROM A RETRACTED POSITION AND A PROJECTEDPOSITION, FIRST CONDUIT MEANS INCLUDING A FIRST VALVE FOR SUPPLYING APRESSURIZED LIQUID ADDITIVE TO SAID SPRAY TUBE, SECOND CONDUIT MEANSINCLUDING A SECOND VALVE FOR SUPPLYING PRESSURIZED AIR TO SAID SPRAYTUBE, SUPPLY MEANS INCLUDING CONTROL MEANS FOR SUPPLYING PRESSURIZED AIRTO SAID AIR OPERATED MEANS AND SAID SECOND CONDUIT MEANS, COACTING MEANSON SAID SPRRAY TUBE AND SAID FIRST AND SAID SECOND VALVE FOR ENGAGINGAND CLOSING SAID SECOND VALVE AND THEREAFTER ENGAGING AND OPENING SAIDFIRST VALVE IN RESPONSE TO THE PROJECTING TRAVEL OF SAID SPRAY TUBE ANDFOR CLOSING SAID FIRST VALVE AND OPENING SAID SECOND VALVE IN RESPONSETO THE RETRACTING TRAVEL OF SAID SPRAY TUBE, PRESSURE ACCUMULATING MEANSDISPOSED IN COMMUNICATION WITH SAID SUPPLY MEANS AND SAID SECOND CONDUITMEANS FOR ACCUMULATING AIR UNDER PRESSURE UPON CLOSING OF SAID SECONDVALVE AND FOR DISCHARGING THE ACCUMULATED AIR AND PURGING SAID SPRAYTUBE UPON THE OPENING OF SAID SECOND VALVE.